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Public release date: 17-May-2010
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Contact: Fariss Samarrai

434-924-3778
University of Virginia
Invasive kudzu is major factor in surface ozone pollution, study shows

Kudzu, an invasive vine that is spreading across the southeastern United
States and northward, is a major contributor to large-scale increases of
the pollutant surface ozone, according to a study published the week of
May 17 in the journal Proceedings of the National Academy of Sciences.
Kudzu, a leafy vine native to Japan and southeastern China, produces the
chemicals isoprene and nitric oxide, which, when combined with nitrogen
in the air, form ozone, an air pollutant that causes significant health
problems for humans. Ozone also hinders the growth of many kinds of
plants, including crop vegetation.
"We found that this chemical reaction caused by kudzu leads to about a
50 percent increase in the number of days each year in which ozone
levels exceed what the Environmental Protection Agency deems as
unhealthy," said study co-author Manuel Lerdau, a University of Virginia
professor of environmental sciences and biology. "This increase in ozone
completely overcomes the reductions in ozone realized from automobile
pollution control legislation."
Lerdau and his former graduate student, lead author Jonathan Hickman *
now a postdoctoral fellow at Columbia University * used field studies at
three sites in Georgia to determine the gas production of kudzu. They
then worked with Shiliang Wu and Loretta Mickley, atmospheric scientists
at Harvard University, who used atmospheric chemistry computer models to
evaluate the potential 50-year effect of kudzu invasion on regional air
quality.
"Essentially what we found is that this biological invasion has the
capacity to degrade air quality, and in all likelihood over time lead to
increases in air pollution, increases in health problems caused by that
air pollution, and decreases in agricultural productivity," Lerdau said.
"This is yet another compelling reason to begin seriously combating this
biological invasion. What was once considered a nuisance, and primarily
of concern to ecologists and farmers, is now proving to be a potentially
serious health threat."
Ozone acts as an irritant to the eyes, nose and throat, and can damage
the lungs, sometimes causing asthma or worsening asthma symptoms. It
also is a mutagen and can cause lung cancer.
Ozone, while essential to the health of the Earth in the upper
atmosphere where it shields the surface from excess ultraviolet
radiation, is hazardous to human health when it forms at the earth's
surface. This occurs most often in the summertime as plants grow and
produce chemicals that react with the air.
Introduced to the United States in the late 19th century, kudzu, with
its unique nitrogen-fixing physiology, allows a rapid, nearly
uninhibited rate of growth, about three times the rate of trees and
other vegetation. The vine was cultivated more extensively in the 1920s
and 1930s as a control for soil erosion and rapidly became known as "the
vine that ate the South."
In recent, milder winters, Kudzu has expanded its range northward into
Pennsylvania and New York.
"What was once a Southern problem is now becoming an East Coast issue,"
Lerdau said.
Various strategies are used for controlling and eradicating kudzu,
including livestock grazing, burning, mowing and herbicides.

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